diff --git a/Cargo.toml b/Cargo.toml
index a35d145..d83354a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -31,7 +31,7 @@ axum = "0.7"
 criterion = "0.5"
 futures = "0.3"
 http-types = "2"
-pyo3 = "0.22"
+pyo3 = "0.27"
 quickcheck = "1"
 rand = "0.8.4"
 tide = "0.16"
diff --git a/src/encoding/text.rs b/src/encoding/text.rs
index dcd97b5..fd050f4 100644
--- a/src/encoding/text.rs
+++ b/src/encoding/text.rs
@@ -1251,21 +1251,21 @@ mod tests {
     }
 
     fn parse_with_python_client(input: String) {
-        pyo3::prepare_freethreaded_python();
+        pyo3::Python::initialize();
 
         println!("{input:?}");
-        Python::with_gil(|py| {
-            let parser = PyModule::from_code_bound(
+        Python::attach(|py| {
+            let parser = PyModule::from_code(
                 py,
-                r#"
+                c"
 from prometheus_client.openmetrics.parser import text_string_to_metric_families
 
 def parse(input):
     families = text_string_to_metric_families(input)
     list(families)
-"#,
-                "parser.py",
-                "parser",
+",
+                c"parser.py",
+                c"parser",
             )
             .map_err(|e| e.to_string())
             .unwrap();
diff --git a/src/metrics/counter.rs b/src/metrics/counter.rs
index 7016c36..c4cecd2 100644
--- a/src/metrics/counter.rs
+++ b/src/metrics/counter.rs
@@ -265,7 +265,7 @@ mod tests {
                 // Map infinite, subnormal and NaN to 0.0.
                 .map(|f| if f.is_normal() { f } else { 0.0 })
                 .collect();
-            let sum = fs.iter().sum();
+            let sum: f64 = fs.iter().sum();
             let counter = Counter::<f64, AtomicU64>::default();
             for f in fs {
                 counter.inc_by(f);